Manual of Petroleum Measurement Standards Chapter 12.2

Calculation of Petroleum Quantities Using Dynamic Measurement Methods and Volumetric Correction Factors

SECOND EDITION, JULY 2021

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Foreword

API MPMS Chapter 12.2, 2nd Edition, Calculation of Petroleum Quantities Using Dynamic Measurement Methods and Volumetric Correction Factors, supersedes the following standards, all of which are withdrawn:

• API MPMS Chapter 12.2.1, 2nd Edition 1995, Calculation of Petroleum Quantities Using Dynamic Measurement Methods and Volumetric Correction Factors—Part 1—Introduction

  
  

• API MPMS Chapter 12.2.2, 3rd Edition 2003, Calculation of Petroleum Quantities Using Dynamic Measurement Methods and Volumetric Correction Factors—Part 2—Measurement Tickets

  
  

• API MPMS Chapter 12.2.3, 1st Edition 1998, Calculation of Petroleum Quantities Using Dynamic Measurement Methods and Volumetric Correction Factors—Part 3—Proving Reports

  
  

  Revision of other parts of API MPMS Chapter 12.2 is ongoing. It is anticipated that:

  
  

• API MPMS Chapter 12.2.4, 1st Edition 1997, Calculation of Petroleum Quantities Using Dynamic Measurement Methods—Part 4—Calculation of Base Prover Volumes by Waterdraw Method, will be superseded by API MPMS Chapter 12.4.1, Calculation of Petroleum Quantities—Base Prover Volume Determination—Waterdraw Volumetric Method

  
  

• API MPMS Chapter 12.2.5, 1st Edition 2001, Calculation of Petroleum Quantities Using Dynamic Measurement Methods—Part 5—Calculation of Base Prover Volumes by Master Meter Method, will be superseded by API MPMS Chapter 12.4.2, Calculation of Petroleum Quantities—Base Prover Volume Determination—Master Meter Method

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Contents

Page

1. Scope 1

2. Normative References 1

3. Terms, Definitions, Symbols, and Abbreviations 1

   1. Terms and Definitions 1

   2. Symbols and Abbreviations 3

4. Field of Application 8

   1. Applicable Fluids 8

   2. Reference, Standard, and Base Conditions 8

   3. Defined Tolerances 8

5. Uncertainty 8

6. Precision, Rounding, and Averaging 8

   1. Outline of Calculations 8

   2. Register Precision and Rounding 9

   3. Averaging 9

7. Discrimination Levels and Discrimination Tables 10

8. Liquid Density 14

9. Correction Factors 15

   1. Overview 15

   2. Liquid Density Correction Factors 15

   3. Combined Correction Factors (CCF) 16

   4. Correction for Sediment and Water (CSW) 16

   5. Steel Correction Factors 17

   6. K Factor (KF) and Nominal K Factor (NKF) 18

10. Generalized Equations for Liquid Volume Determinations 19

    1. General 19

    2. Determination of Indicated Volume (IV) 19

    3. Determination of Indicated Standard Volume (ISV) 20

    4. Determination of Gross Volume (GV) 20

    5. Determination of Gross Standard Volume (GSV) 20

    6. Determination of Net Standard Volume (NSV) 21

    7. Determination of S&W Volume (SWV) 21

11. Measurement Tickets 22

    1. General 22

    2. Calculation Sequence Flowchart 22

12. Meter Proving Reports 24

    1. Overview 24

    2. Meter Factor and K Factor Calculation—Intermediate Factor and Average Data Methods 24

    3. Evaluating Meter Proving Run Data 26

    4. Recording of Field Data 27

    5. Proving Reports 27

       Contents

       Page

    6. Calculation Sequences 30

Annex A (informative) Reference, Standard, and Base Conditions 34

Annex B (informative) Defined Tolerances Scenarios 36

Annex C (informative) Water in Oil Density Impacts 39

Annex D (informative) Measurement Ticket Examples 40

Annex E (informative) Proving Report Examples 45

Annex F (informative) Repeatability Calculation Examples 54

Annex G (informative) Random Uncertainty of a Meter Factor Determined by Multiple Run Sets 55

Bibliography 57

Figures

1. Calculation Sequence Flowchart 23

2. Calculation Sequence Displacement Provers with Average Data and Spot Sample 30

3. Calculation Sequence Displacement Provers with Intermediate Factor and Online Densitometer 31

4. Calculation Sequence Atmospheric Tank Provers with Intermediate Factor and Spot Sample 32

5. Calculation Sequence Master Meter Provers with Intermediate Factor and Spot Sample 33

1. Crude Oil, Hydrometer, Meter Factor 41

2. Gasoline, Densitometer, Meter Factor 42

3. Jet, Hydrometer, Composite Meter Factor 43

4. Diesel, Hydrometer, Temperature Compensated, Composite Meter Factor 44

E.1a Displacement Prover, Average Data, Fixed Range, Spot Sample 46

E.1b Displacement Prover, Average Data, Fixed Range, Spot Sample 47

E.2a Captive Displacer Prover, Intermediate Factor, Online Density 48

E.2b Captive Displacer Prover, Intermediate Factor, Online Density 49

E.3a Tank Prover, Intermediate Factor, Fixed Range, Spot Sample 50

E.3b Tank Prover, Intermediate Factor, Fixed Range, Spot Sample 51

E.4a Master Meter, Intermediate Factor, Moving Range, Spot Sample 52

E.4b Master Meter, Intermediate Factor, Moving Range, Spot Sample 53

G.1 Multiple Run Set Scenarios with Uncertainty Calculations 56

Tables

1. Liquid Density Discrimination Levels 11

2. Dimensional Discrimination Levels 11

3. Temperature Discrimination Levels 11

4. Pressure Discrimination Levels 12

5. Discrimination Levels of Coefficients of Thermal Expansion 12

   Contents

   Page

6. Modulus of Elasticity Discrimination Levels (E) 13

7. Correction Factor Discrimination Levels 13

8. Volume Discrimination Levels 14

9. Pulse Discrimination Levels 14

B.1 Comparison between the Discrete and Continuous Methods 37

C.1 Water in Oil Density Impacts 39

1. Consecutive Runs and the Average Data Method 54

2. Consecutive Runs and the Intermediate Factor Method 54

Introduction

This standard presents the calculation procedures for dynamic measurement tickets (meter tickets), and meter proving of devices with volumetric outputs.

Earlier versions of this standard were written when mechanical desk calculators and tabulated values were widely used for calculating measurement documentation. Rules for rounding and the choice of how many figures are required for each calculation step were often made on the spot, which could result in different operators obtaining different results from the same data. Introduction of computers and solid-state scientific desk calculators improved the process, but different manufacturers’ machines often produced slightly different results. To address this problem, the previous version of this standard rigorously specified the equations for computing correction factors, rules for rounding, calculation sequence, and the discrimination levels employed with the purpose of standardizing calculations to produce the same unbiased answer from given data. The implementation procedures presented in this standard are designed to use computer technology, simplify the associated arithmetic operations, and incorporate current API MPMS Chapter 11 [4] standards.

This standard does not address the differences in the raw/measured data due to differences in the precision of the instrumentation and the collection of its data. Therefore, if a continuous data system is being used on the same stream and redundant with a discrete data system to collect and process measured quantities, it is not expected that they would necessarily produce identical results. It is expected that they both be in compliance with the guidelines in API MPMS Chapter 21.2 [10] and the requirements of this standard.

This standard presents two methods for data acquisition:

1. Discrete Method (Traditional Method)

   
   

2. Continuous Method (Dynamic Method)

In the Discrete Method, flow-weighted averages of temperature, pressure and density are used to correct the total actual volume at operating conditions for the entire ticket period, as measured by the flow meter and corrected by the meter factor, to what that total actual volume would be at standard temperature and pressure conditions for the entire ticket period. Thus, the total indicated volume for the entire ticket period is corrected by the meter factor to determine the total gross volume for the entire ticket period; and, then the total gross volume is corrected to the gross standard volume for the entire ticket period.

In the Continuous Method, the process variables of density, temperature and pressure are sampled every scan cycle and the indicated volume of the meter is determined for each scan cycle as well. In the Continuous Method, temperature, pressure, and density are used to correct the incremental gross volume for each scan cycle period. Thus, the total indicated volume for any given scan cycle period is corrected by the meter factor to determine the total gross volume for that scan cycle period; and, then the total gross volume is corrected to the gross standard volume for that same given scan cycle period. The incremental gross standard volumes determined for each scan cycle or sampling period would be summed on an accumulative basis for the entire measurement or ticket period to yield the total gross standard volume for the entire batch.

In either data acquisition method, the same calculation routines are used. The only difference is intermediate rounding

and the time in which the calculation is performed.

Volumetric calculations and process variable acquisitions in the Continuous Method are not continuous, but “near” continuous. As scan times in flow computers decrease, the process variable acquisition increases and will be closer to continuous.

When a ticket has been calculated by a flow computer using the Continuous Method, the reported data can be used to make a calculation comparison using the Discrete Method. When this is done, the flow-weighted average temperature, pressure and observed density is used to calculate the flow-weighted average base density. The discrimination levels

of temperature, pressure and density should be the same as those reported on the Continuous Method report for comparison purposes. These two methods might yield slightly different results due to the different rounding routines employed and the way the data are acquired and processed.

Rounding or truncating initial and intermediate values in the Continuous Method has been eliminated.

Reporting discrimination is only applied to the measurement ticket reported values; thus, older computer processor technology or manual calculations may not reproduce the same exact results as modern machines or manual calculations using this revised standard. Unrounded numbers in no way imply measurement accuracies to those levels. Measurement accuracies are solely dependent upon each measurement device. Identical input data should give different users equivalent results.

The intent of this document is to serve as a rigorous standard. Examples are provided to aid the user in checking computations developed using the requirements of this standard.

Calculation of Petroleum Quantities Using Dynamic Measurement Methods and Volumetric Correction Factors

1. Scope

   
   

   This document provides standardized calculation methods for the quantification of liquids, regardless of the point of origin or destination or the units of measure required by governmental customs or statute. The criteria contained in this document allow different entities using various computer languages on different computer hardware (or manual calculations) to arrive at output results within a defined tolerance within this document, using the same input data.

   
   

   The document rigorously specifies the equations for computing correction factors, rules for rounding, calculation sequence, and discrimination levels to be employed in the calculations. No deviations from these specifications shall be permitted since the intent of this document is to serve as a rigorous standard. This document also covers multiple calculations as required by dynamic, online, integrated, continuous flow measurement.

   
   

2. Normative References

The following reference documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document applies (including any addenda or errata, or both).

API MPMS Chapter 13 (All Sections), Statistical Aspects of Measuring and Sampling

3 Terms, Definitions, Symbols, and Abbreviations

3.1 Terms and Definitions

For the purposes of this document the following terms and definitions apply. Terms of more general use may be

found in the API MPMS Chapter 1—Online Terms and Definitions Database.

3.1.1

absolute density

The mass of a substance per unit of volume at a specified temperature and pressure.

3.1.2

composite meter factor CMF

A meter factor, adjusted at the time of proving, from assumed normal operating meter pressure during the ticket period to base pressure, when it is desired to not have to calculate the correction for compressibility at the time of the measurement ticket calculation, and where it is assumed that the pressure, temperature, and density are constant during the ticket period.

3.1.3

flow computation device

An arithmetic processing unit with associated memory that accepts electrically converted signals representing input variables from a liquid measurement system and performs calculations for the purpose of providing flow rate and total quantity data. It is sometimes referred to as a flow compilation device, flow computer, or tertiary device.

3.1.4

gross volume GV

The actual volume of fluids at flowing temperature and pressure as measured by a meter.

1